"In Sweden it's not allowed to say good things about yourself," John Guidetti explains. "You're not allowed to dream. People used to ask me: 'What's your biggest dream?' I wanted to be the best football player in the world. That was my dream. Except in Sweden it's not accepted. 'Who does he think is?' they'd say. 'He should stop talking.' But who is someone to say I'm not allowed to dream? A dream is a dream, not necessarily reality, and if I could wish for anything, that would be my ultimate dream. I don't want a pool full of candy. I'd want to the best footballer in the world."

He's not an ordinary John. It doesn't take long to spot the Zlatan-levels of self-confidence, and before anyone suggests he might need bringing down a peg or two it is worth pointing out he is quite accustomed to people questioning whether he can walk the walk.

It is why his friends have suggested that when he finishes his career he opens a flower shop. "We'd call it Flowers for Doubters and send flowers to all the people who doubted me. All those people, they don't realise they drive me on. The flowers would be a little thank you."

We are talking in an upstairs room at Stoke City's training ground, where he is on loan from Manchester City, slowly rebuilding his career after the freakish illness that halted his sharp, upward trajectory as one of the outstanding young talents in his sport.

There is an irony here because there will no doubt be people reading this who have never even seen Guidetti on a football pitch, and suspecting a touch of the Nicklas Bendtner syndrome. Yet the people who have followed Guidetti's career will testify that this is a player of rare gifts. It is just that, so far, they have largely been kept from English football.

Mark Hughes, who knows a thing or two about strikers, intends to use the 21-year-old in Stoke's FA Cup tie at Chelsea on Sunday. Roberto Mancini is another admirer. One of Mancini's early fall-outs at Manchester City came in 2011 when he discovered the club had let Guidetti reach the end of his development contract. "I'd signed a pre-contract with Twente," Guidetti recalls. "Mancini intervened. He went to the club and said: 'Where's John?' City said: 'We let him go.' And Mancini said: 'No, no, what are you doing?' Lawyers had to get involved. I have a lot of respect for Mancini. He liked me as a player."

It was the following season, when Guidetti moved on loan to Feyenoord, that it became apparent there was more to him than – by his admission – having "a big mouth". At 19, he tore through the Eredivisie, scoring 20 times in 23 games, including hat-tricks against Ajax, Vitesse and Twente. His manager, Ronald Koeman, described him as "phenomenal".

"There were supporters getting tattoos of my name. Every home game, 50,000 people, on their feet, shouting 'Super Guidetti'. Everyone doing this [mimicking a two-handed bowing-down gesture]. They made a rap song and put me in it. 'Look at Messi, we have Guidetti.' It was amazing, the best year of my life."

He talks about this period at 100 words per minute. "Life was amazing. I was heading for the European Championship with Sweden. I was trying to be the top scorer in Holland. One of the newspapers had given me their player-of-the-year award. I was going to be the youngest Swedish player in history to go to the European Championship, in contention to start every game, alongside a great player like Zlatan Ibrahimovic. I was flying. Everything was amazing.

"But then we got to my 20th birthday. My girlfriend and some friends had organised a surprise party. They rented a restaurant and part of a nightclub. But I started to feel bad, really shit. I said to everyone: 'Listen, stay and party, you've done it beautifully, but I have to go home.' That was midnight. I woke up in the night puking. The manager was fuming with me because he thought I'd been partying but, no bullshit, I've never had a drop of alcohol in my life.

"I was out with this stomach virus for 10 days and when I went back to training I couldn't stand on my right leg. I just kept falling over. I was thinking: 'It's sleeping, man, why is my leg sleeping?' They said: 'Go on the bike, try to warm it up.' It didn't work. I tried to put my jeans on and fell over. I tried to put my pants on, fell straight back and hit my head. I couldn't stand. I had no balance. That's when they took me to hospital."

The doctors suspect the original illness was from a piece of infected chicken, and that the reaction was caused by the antibodies inside his stomach attacking both the virus and his nerve system, paralysing his right leg. "It knocked out the nerve system. The nerve needed to regrow and that takes longer than a wound or a muscle. Meanwhile, the problem is you lose muscle because you can't do anything with your leg. I lost all the strength in it. I couldn't stand on it. I couldn't do anything. They gave me this medicine to flush out my body and then literally it was all about waiting."

In total, he has missed nearly two years of football. "It's going to take a bit of time because you don't just go straight back and boom [clicks fingers]. I was working for 19 years to become what I was before. But I feel good. I just need to play games. You hear all these things - 'John's career is over,' la, la, la, la – and it's scary. I love football more than anything in the world. People care about certain things. Me? What I care about is scoring a goal in front of 50,000 people, all screaming your name. It's the best feeling in the world and I've missed it. I get goosebumps just thinking about it."

It is some story. Yes, Guidetti is not lacking in self-confidence, but he is a fascinating guy. Worldly, too, as might be expected of someone who spent two chunks of his childhood living just outside Nairobi and playing street football in Kibera, the largest urban slum in eastern Africa.

His father, Mike, had moved the family to Kenya to help with a schools project. "I loved it," Guidetti says. "My favourite place on earth. I tell everyone I want to live in Kenya when my career is finished. People say: 'You're crazy, you could live anywhere and you want to live there?' I say: 'Listen, it's the best place in the world.'"

He has set up the John Guidetti Foundation, which will build football pitches and schools in Kenya, and he scrolls through his phone to find a brilliant photograph of himself – a skinny little boy with a mop of blond hair – in a sea of black faces from his first club, the Black Stars Kibera. What age range? I ask, and then immediately realise it was a mistake. He smiles. "There aren't many passports, my friend."

His debut for Stoke came as a substitute at Crystal Palace last weekend. "I said to the Swedish media afterwards: 'If I had been on another 10 minutes, I was going to score.' I knew I was going to score. I felt it in my body and I'm not usually wrong. I score goals, that's what I do. I give energy. I went to Feyenoord and they said I made them believe again. That's what I do."

It is probably no surprise he polarises opinion back in Sweden. But surely, I ask, a nation that cherishes Ibrahimovic – the man who said the World Cup would not be worth watching if he were not involved – should embrace him, too?

"Zlatan?" he replies. "Trust me – just lately, people like him. Before that, nobody liked him. I'm telling you, in Sweden it's not allowed to talk about yourself in a good way. But you're always going to have doubters, people who say you're not good enough, you can't do this and can't do that. Plus I do talk a lot. I speak my mind. I go to Holland and say I'm going to score 20 goals. And I do it. You get injured for two years and you see people saying: 'He's nothing.' That's Flowers for Doubters, man. The people who say you can't make it – you're going to eat your words."